Subj : Re: Exceptions and Object Lifetimes
To   : netscape.public.mozilla.jseng
From : "Pete Diemert" <pete.diemert@purposebuilt.com.au>
Date : Wed Dec 17 2003 11:39 am

Actually found the answer to #1 below (my bug, was setting exception info
properly but was not returning JS_FALSE from our native ctor, therefore no
throw).

However, any thoughts on #2 are still much appreciated.


"Pete Diemert" <pete.diemert@purposebuilt.com.au> wrote in message
news:bro6ne$es52@ripley.netscape.com...
>
> Hello, this is my first post to this group, if I am posting in the wrong
> place please let me know.  We have been working to embed the Spidermonkey
> 1.5 engine with great progress however there are a couple of issues that
> have sprung up which I can't seem to locate the answers for:
>
> 1)  Exceptions - We have exposed our own object/funcs and so, would also
> like to expose errors that our functions can generate as catchable
> exceptions in JS.  However, from looking at JSAPI.H we cannot see a clear
> way to "throw" an exception from the host.  We have tried to add entries
to
> JS.MSG and marked them as JSXN_ERR which seems to cause the exception
object
> to get generated in scope but alas nothing is catching in JS.  Do we have
to
> actually construct JS script to do the throw then evaluate the script in
> scope in order to get exceptions?
>
> 2)  Object Lifetimes - To make the object model in JS coherent with our
own
> internal object model we allow the JS object to keep a "reference count"
on
> our internal object so that JS controls its lifetime.  This works fine but
> we notice that the GC is VERY lazy and will choose to keep objects alive
> after they are clearly never going to be accessed again, waiting for
> shutdown or mem threshold, e.g.:
>
> function foo()
> {
>     var x = new SomeObject;
>     // x drops out of scope after func, never to be seen again but object
> ref will remain
> }
>
> The object does indeed get cleaned up at shutdown but we have a system
that
> may instantiate some fairly big footprint objects such as forms,
databases,
> recordsets, etc...  Understanding that the GC reserves the right to
> arbitrarily clean these objects is there some way we can get a callback
> stating "object no longer in use by any call object" in lieu of a
> JSFinalize() so that we can force the GC ourselves and prevent a rather
> large uneeded working set?
>
> Any insight or pointers in the right direction would be helpful including
> more searchable resources like this newsgroup.
>
> thanks,
> Pete Diemert
>
>

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